IDL grammar

Learn about the syntax of IDL files in a formal notation.

An IDL file contains definitions of the interface between client and server. The IDL file is used by EntireX wrappers to generate RPC clients, RPC servers and tester etc. on the basis of these definitions. The IDL file can be edited by the IDL Editor provided by plug-ins for Eclipse.

Meta definitions

The following metasymbols are used to define the IDL:
  • The metasymbols [ and ]enclose optional lexical entities.
  • The metasymbols { and } enclose optional lexical entities which may be repeated a number of times.
  • The metasymbol ::= separates the lexical entity to be defined (on the left) from the definition (on the right).
  • The metasymbol | separates lexical entities on the definition side (on the right) meaning all terms are valid to define the lexical entity to be defined (on the left).
The following basic terms are used to describe the IDL:
  • The informal term number is a sequence of numeric digits. Example, 123.
  • The informal term string is a sequence of characters. It can contain any character except enclosing apostrophes.

    Examples are: 'DARMSTADT' '#FRANKFURT' '&MUNICH'.

  • Any terms in uppercase, special characters such as apostrophe, colon (other than the metasymbols above) are terminal lexical entities and must be entered as is.
  • The term identifier is built by a sequence of characters from a defined list:
    • characters: a to z
    • characters: A to Z
    • digits: 0 to 9 (a digit must not be the first character)
    • special characters: - _ $ # & @ + / £ æ Æ ø Ø å Å

See Rules for coding group and parameter names.

Syntax of the IDL file

Syntax

EntireX IDL::= library-definition { library-definition }

Description

  • The IDL may contain any number of library-definitions.
  • One library-definition must be contained in an IDL file.

library-definition

A library-definition is the grouping of servers (remote procedures).

Syntax
Table 1. Syntax - library-definition
Parameter Description
library-definition ::= LIBRARY 'library-name' [:'library-alias'] IS { interface }
library-name ::= string
library-alias ::= string
interface ::= program-definition | structure-definition
Description
Table 2. Parameters - library-definition
Parameter Description
library-definition A library-definition is valid until the next library-definition or end of file.
library-name
  • The library-name is used to generate RPC components. How this takes place (e.g. to form a source file name, class name etc.) depends on the target programming language. The wrappers will adapt the library-name to the requirements of the target programming language when special characters occur in the library-name.

    See Mapping library name and alias to C | COBOL | .NET | Java | Natural | PL/I.

  • The library-name is also sent (without modifying any special characters) from the RPC client component to the RPC server. In the RPC server the library-name may be used to locate the target server.

    See Locating and calling the target server under z/OS (CICS, Batch, IMS) | C | .NET.

  • Certain rules apply to library-name. See Rules for coding library, library alias, program, program alias and structure names.
library-alias
  • Alias of the library-name.
  • The purpose of an alias is to allow a different name on the RPC client side from the name on the RPC server side. This is helpful when integrating a system with a short name (e.g. CICS, z/OS, Natural, where up to 8 characters are allowed, or IBM i, where up to 10 characters are allowed) on one side and on the other side an environment with fewer restrictions (Linux, Windows, Java).
  • The library-alias may be used as a name in the target programming language to form the generated RPC client and RPC server components instead of the library-name. How the library-alias is used to generate components (e.g. to form a source file name, class name etc.) depends on the target programming language.

    See Mapping library name and alias to C | COBOL | .NET | Java | Natural | PL/I.

  • The library-alias is always used as is (it is not adapted by the IDL Editor and the Designer wrappers when special characters occur within the library-alias as it is for the library-name), i.e. the user is responsible for a valid target programming language name.
  • The library-alias is not sent to the target RPC server. The library-name is always sent instead.
  • Certain rules apply to library-name. See Rules for coding library, library alias, program, program alias and structure names.
interface
  • A program-definition or structure-definition concludes the library-definition.
  • Any number of program-definitions or structure-definitions can be embedded in a library-definition.
Example (without alias usage)
Library 'ServerLibrary' Is ..
Example (with alias usage)
Library 'ServerLibrary': 'AliasServerLibrary' Is ..

program-definition

A program-definition describes the parameters of servers (remote procedures).

Syntax
Table 3. Syntax - program-definition
Parameter Description
program-definition ::= PROGRAM 'program-name' [:'program-alias'] IS parameter-data-definition
program-name ::= string
program-alias ::= string
Description
Table 4. Parameters - program-definition
Parameter Description
program-definition
  • A program-definition is valid until the next program-definition, structure-definition, library-definition or end of file.
  • Any program-definition must be embedded in a library-definition.
  • Any number of program-definitions can be embedded in a library-definition.
  • One parameter-data-definition must conclude the program-definition.
program-name
  • The program-name is used to generate RPC components. How this takes place (e.g. how to form a source file name, method, function or program name etc.) depends on the target programming language. The IDL Editor and the integrated Designer wrappers will adapt the program-name to the requirements of the target programming language when special characters occur in the program-name.

    See Mapping program name and alias to C | COBOL | .NET | Java | Natural | PL/I.

  • The program-name is also sent (without modifying any special characters) from the RPC client component to the RPC server. In the RPC server the program-name is used to locate the target server.

    See Locating and Calling the Target Server under z/OS (CICS, Batch, IMS) | C | .NET.

  • Certain rules apply to program-name. See Rules for coding library, library alias, program, program alias and structure names .
program-alias
  • Alias of the program-name.
  • The purpose of an alias is to allow a different name on the RPC client side from the name on the RPC server side. This is helpful when integrating a system with a short name (e.g. CICS, z/OS, Natural, where up to 8 characters are allowed, or IBM i, where up to 10 characters are allowed) on one side and on the other side an environment with fewer restrictions (Linux, Windows, Java).
  • The program-alias may be used as a name in the target programming language to form the generated RPC client and RPC server components instead of the program-name. How the program-alias is used to generate components (e.g. to form a source file name, method, function or program name etc.) depends on the target programming language.

    See Mapping program name and alias to C | COBOL | .NET | Java | Natural | PL/I.

  • The program-alias is always used as is (it is not adapted by the IDL Editor and the wrappers when special characters occur within the program-alias as it is for the program-name), i.e. the user is responsible for a valid target programming language name.
  • The program-alias is not sent to the target server. The program-name is always sent instead.
  • Certain rules apply to program-alias. See Rules for coding library, library alias, program, program alias and structure names.
Example (without alias usage)
Library 'ServerLibrary' Is
    Program 'ServerName' Is ..
Example (with alias usage)
Library 'ServerLibrary': 'AliasServerLibrary' Is
       Program 'ServerName' : 'AliasServerName' Is ..

structure-definition

A structure-definition describes a user-defined type for reusability, referenced in a structure-parameter-definition(IDL).

Syntax
Table 5. Syntax - structure-definition
Parameter Description
structure-definition ::= STRUCT 'structure-name' IS parameter-data-definition
structure-name ::= string
Description
Table 6. Parameters - structure-definition
Parameter Description
structure-definition
  • A structure-definition is valid until the next program-definition, structure-definition, library-definition or end of file.
  • Any structure-definition must be embedded in a library-definition.
  • Any number of structure-definitions can be embedded in a library-definition.
  • One parameter-data-definition must conclude the structure-definition.
  • Structures are mapped to various concepts depending on the target programming language. See Mapping Structures to C | COBOL | .NET | Java | Natural | PL/I.
structure-name
Example
Library 'ServerLibrary': 'AliasServerLibrary' Is
Struct 'Person' Is ..

parameter-data-definition

The parameter-data-definition describes the parameters of a server when it is embedded in a program-definition. It describes a user-defined type when it is embedded in a structure-definition.

Syntax
Table 7. Syntax - parameter-data-definition
Parameter Description
parameter-data-definition ::= DEFINE DATA PARAMETER simple-parameter-definition | group-parameter-definition | structure-parameter-definition { simple-parameter-definition | group-parameter-definition | structure-parameter-definition } END-DEFINE
Description
Table 8. Parameters - parameter-data-definition
Parameter Description
parameter-data-definition
  • The parameter-data-definition consists of a starting token sequence (Define Data Parameter) and an ending token sequence (End-Define).
  • Any number of simple-parameter-definition, group-parameter-definition and structure-parameter-definition can be embedded in a parameter-data-definition.
  • At least one simple-parameter-definition, group-parameter-definition or structure-parameter-definition must exist (at level 1) without the attribute-list.
  • The parameter-data-definition must conclude the corresponding program-definition or structure-definition.
  • There can only be one parameter-data-definition for each program-definition or structure-definition.
Example of a program
Library 'ServerLibrary' Is
        Program 'ServerName' Is ..
                Define Data Parameter
                ...
                End-Define
Example of a structure
Library 'ServerLibrary': 'AliasServerLibrary' Is
         Struct 'Person' Is ..
                Define Data Parameter
                ...
                End-Define

simple-parameter-definition

The construct simple-parameter-definition describes the syntax of a simple parameter, that is, not a group (groups are described in a group-parameter-definition), not a reference to a structure (referencing a structure is described in structure-parameter-definition(IDL)).

Syntax
Table 9. Syntax - simple-parameter-definition
Parameter Description
simple-parameter-definition ::= level parameter-name (type-length[/array-definition]) [attribute-list]
level ::= number
parameter-name ::= identifier
type-length See IDL Data Types.
Description
Table 10. Paramters - simple-parameter-definition
Parameter Description
level
  • Level number is a 1 or 2-digit number in the range from 01 to 99 (the leading 0 is optional) used in conjunction with parameter grouping.
  • Parameters assigned a level number of 02 or greater are considered to be members of the immediately preceding group that has been assigned a lower level number.
  • Do not skip level numbers when assigning the level numbers for group members.
parameter-name
  • The name of the parameter. The parameter-name is used as name in the target programming language. It is adapted by the IDL Editor and the wrappers to the requirements of the target programming language.

    See Mapping parameter names to C | COBOL | .NET | Java | Natural | PL/I.

  • Certain rules apply to parameter-name. See Rules for coding group and parameter names.
type-length The type and length of the parameter. See IDL Data Types.
Example
...
  1 PERSON-ID (N10)
  1 PERSON-NAME (A100)
...

group-parameter-definition

The construct group-parameter-definition describes the syntax of a group.

Syntax
Table 11. Syntax for group-parameter-definition
Parameter Description
group-parameter-definition ::= level group-name [(/array-definition)] [attribute-list]
level ::= number
group-name ::= identifier
Description
Table 12. Paramter for group-parameter-definition
Parameter Description
level See simple-parameter-definition.
group-name
  • The name of the group.
  • The definition of a group enables references to a series of parameters (can also be only 1 parameter) by using the group name.

    This provides a convenient and efficient method of referencing a series of consecutive parameters.

  • A group may contain other groups, structures (structure-parameter-definition) or parameters (simple-parameter-definition) as group members.
  • Certain rules apply to group-name. See Rules for coding group and parameter names.
  • Groups are mapped to various concepts depending on the target programming language.

    See Mapping Groups and Periodic Groups to C | COBOL | .NET | Java | Natural | PL/I.
Example
...
1 PERSON /* this is the group */
2 PERSON-ID (N10) /* this is a group member */
2 PERSON-NAME (A100) /* this is also a group member */
...

structure-parameter-definition (IDL)

The construct structure-parameter-definition describes the syntax of a reference to a structure.

Syntax
Table 13. Syntax for structure-parameter-definition (IDL)
Parameter Description
structure-parameter-definition ::= level parameter-name (structure-reference[/array-definition]) [attribute-list]
level ::= number
parameter-name ::= identifier
structure-reference ::= 'structure-name'
Description
Table 14. Paramters for structure-parameter-definition (IDL)
Parameter Description
level See simple-parameter-definition.
parameter-name See simple-parameter-definition.
structure-reference
Example
STRUCT 'Person' Is /* this defines the structure person */
Define Data Parameter
1 PERSON
2 PERSON-ID (N10)
2 PERSON-NAME (A100)
End-Define
...
1 FATHER ('Person') /* this references the structure */
1 MOTHER ('Person') /* this references the structure */
1 CHILDS ('Person'/10) /* this references the structure */
...

array-definition

Arrays can have either fixed upper bounds or variable upper bounds, so-called unbounded arrays.

Syntax
Table 15. Syntax for array-definition
Parameter Description
array-definition ::= fixed-bound-array | unbounded-array
fixed-bound-array ::= [fixed-bound-array-index [,fixed-bound-array-index [,fixed-bound-array-index]]]
unbounded-array ::= [unbounded-array-index [,unbounded-array-index [,unbounded-array-index]]]
fixed-bound-array-index ::= [lower-bound:] upper-bound
unbounded-array-index ::= [1:] V[maximum-upper-bound]
lower-bound ::= number
upper-bound ::= number
maximum-upper-bound ::= number
Description
Table 16. Parameters for array-definition
Parameter Description
array-definition
  • Arrays with a fixed size of elements are fixed bound arrays.
  • Arrays with a variable number of elements are so called unbounded arrays.
  • Arrays are one, two or three-dimensional.
fixed-bound-array
  • Almost all programming languages have a concept of arrays with a fixed size of elements.
  • See Mapping fixed and unbounded arrays to C | COBOL | .NET | Java | Natural | PL/I.
unbounded-array
  • Unbounded arrays are not supported by all endpoints, or are supported with restrictions.
  • See Mapping fixed and unbounded arrays to C | COBOL | .NET | Java | Natural | PL/I.
fixed-bound-array-index
  • If an array-index is of the format [lower-bound:]upper-bound it describes an array with fixed bounds.
  • The fixed number of occurrences is calculated as upper-bound - lower-bound + 1.
unbounded-array-index
  • If maximum-upper-bound is given, the variable number of occurrences (elements) can vary between 0 (empty unbounded array) and maximum-upper-bound.
  • If no maximum-upper-bound is given, there is no practical upper limit on the variable number of occurrences.(1)
  • Empty unbounded arrays with zero number of occurrences are always possible. The optional notation [1:] is ignored and has no effect.

    Note: (1) The implementation limits the number to 2,147,483,647 elements.

  • If an array-index is of the format [1:]V[maximum-upper-bound] it describes an unbounded array with variable bounds.
lower-bound
  • The lower-bound value is optional.
  • If the lower-bound is not given, the default is 1.
upper-bound
  • The upper-bound value must be entered.
  • The upper-bound value must be greater than or equal to the lower-bound.
maximum-upper-bound
  • The maximum-upper-bound value is optional.
  • It defines a limit which cannot be exceeded.
Example of arrays with fixed bounds
...
1 NAMES (A100/10) /* 1 dimensional array */
1 TUPLES (A100/10,10) /* 2 dimensional array */
1 TRIPLES (I1/1:20,1:20,1:20) /* 3 dimensional array */
...
Example of arrays with variable upper-bounds
...
1 NAMES (A100/V) /* 1 dimensional array */
1 TUPLES (A100/V,V) /* 2 dimensional array */
1 TRIPLES (I1/1:V,1:V,1:V) /* 3 dimensional array */
...
Example of arrays with variable upper-bounds and maximum
...
1 NAMES (A100/V10) /* 1 dimensional array */
1 TUPLES (A100/V10,V10) /* 2 dimensional array */
1 TRIPLES (I1/1:V20,1:V20,1:V20) /* 3 dimensional array */
...
CAUTION:
Mixed arrays with fixed upper bounds and variable upper bounds are not supported. (I2/1:V,20,V) is not permitted. (I2/V10,30) is not permitted.
Three-dimensional array with fixed bounds
Three-dimensional array with fixed bounds
Three-dimensional array with variable upper bounds
Three-dimensional array with variable upper bounds
In the illustration, the vectors of the second dimension have different lengths. The first vector has a length of 4, the second a length of 3 and the third a length of 2. The same is true for the third dimension with vector length of (3,4,5,6) (2,4,3) and (4,3).
Note: This type of unbounded array is not possible if you are using COBOL as the endpoint. In COBOL, all vectors in a dimension have the same length. A 2-dimensional array forms a rectangle and a 3-dimensional array forms a cuboid.

attribute-list

Attributes describe further parameter properties to correctly map the parameter to the target platform or to optimize the parameter transfer.

Syntax
Table 17. Syntax for attribute-list
Parameter Description
attribute-list ::= [ aligned-attribute ] [ direction-attribute ] [ ims-attribute ] [ choice-attribute ]
aligned-attribute ::= ALIGNED
direction-attribute ::= IN | OUT | IN OUT | INOUT
ims-attribute ::= IMS
choice-attribute ::= CHOICE
Description
Table 18. Parameters for attribute-list
Parameter Description
aligned-attribute
  • The aligned attribute (mainly) belongs to the server and describes a different alignment from the compiler's default of the server interface.
  • The aligned attribute is relevant for the programming languages COBOL and PL/I in the RPC server environments batch, CICS and IMS.
  • Programming languages other than COBOL and PL/I do not consider it in the interface of the generated servers.
  • RPC Clients send the aligned attribute within the RPC data stream to the RPC server, where it is considered (the related parameter is aligned) by the RPC server, if relevant.
  • See Mapping the ALIGNED Attribute to C | COBOL | .NET | Java | Natural | PL/I for information on whether your client environment supports sending aligned attributes.
direction-attribute The direction attribute optimizes parameter transfer.
  • In data is passed from client to server.
  • Out data is passed from server to client.
  • In Out data is passed in both directions.
  • The direction of group members is inherited from the parent group. Thus only the direction information of the top-level fields (level 1) is relevant. Group fields always inherit the specification from their parent.
  • A different specification given with the group members is ignored.
  • The direction of members of a structure-definition is inherited from the structure-parameter-definition. Thus only the direction information of the structure-parameter-definition (structure reference) is relevant. Structure fields always inherit the specification from their reference.
  • A different specification given with the structure members is ignored.
  • When no direction is specified, In Out is used as the default.
  • See Mapping the Direction Attributes In, Out, InOut to C | COBOL | .NET | Java | Natural | PL/I.
ims-attribute The ims-attribute marks PCB (Program Communication Block) parameters for the target platform IMS (IBM's Information Management System).
  • The ims-attributes are considered when servers for the target platform IMS are generated with the COBOL Wrapper and the PL/I Wrapper.
  • The ims-attributes are obsolete for clients and other wrappers than COBOL and PL/I and are ignored.
  • The ims-attribute is only relevant on top-level fields (level 1). Group fields always inherit the specification from their parent, thus a different specification is ignored.
choice-attribute The choice-attribute marks a group-parameter-definition as the surrounding container for multiple possible output (MPO) structures. This kind of IDL syntax is retrieved when extracting, for example, from a REDEFINES Clause. See also Mapping Editor IDL Interface mapping function Set Multiple Possible Output (MPO) Structures for interface type DFHCOMMAREA (In same as Out, In different to Out) | Large Buffer (In same as Out, In different to Out) | Channel Container | IMS Connect.
Example of aligned-attribute:
1 PERSON_ID (NU12) ALIGNED
Example of direction-attribute:
...
1 PERSON_ID (NU12) IN
1 PERSON_NAME (A100) OUT
...
Example of ims-attribute:
...
1 PERSON_ID         (NU12)  IN OUT
1 PERSON_NAME       (A100)  IN OUT
1 DBPCB             IMS
   2  DBNAME           (A8)
   2  SEG-LEVEL-NO     (A2)
   2  DBSTATUS         (A2)
   2  FILLER           (A20)
...
Example of choice-attribute:
...
1 OUTPUT             Out
  2 PAYMENT-TYPE             (A2)
  2 PAYMENT-DATA-MPO  Choice
   3 PAYMENT-DATA            (/V1)
    4 PAYMENT-DATA           (AV256)
   3 PAYMENT-DATA-VOUCHER    (/V1)
    4 VOUCHER-ORIGIN         (AV128)
    4 VOUCHER-SERIES         (AV128)
   3 PAYMENT-DATA-CREDITCARD (/V1)
    4 CREDITCARD-NUMBER      (NU18)
    4 CREDITCARD-CODE        (NU12)
    4 CREDITCARD-VALIDITY    (AV8)
...